Discuss diffusion through the plasma membrane.
- Because the plasma membrane is a bi-lipid layer, molecules that are small, nonpolar or uncharged, or lipid-soluble pass easily through it. These include:
- -Oxygen, carbon dioxide, and stereoid hormones.
Gas exchange: net diffusion of O2
into cells and CO2
out of cells due to concentration gradients (opposite in lungs).
Water can pass through awesome channels known as aquaporins
Charged ions pass through ion channels that cross the plasma membrane that may always be open or gated
Larger polar molecules can not
pass through the membrane by simple diffusion, but need special carrier proteins.